Wolf-Rayet Stars in M33 II: Optical Spectroscopy of emission-line stars in Giant Hii Regions

TL;DR

This study provides optical spectra of 14 emission-line stars in M33's giant HII regions, confirming the effectiveness of narrow-band imaging for detecting such stars and improving their identification with archival HST data.

Contribution

It offers new spectroscopic data for known and candidate Wolf-Rayet stars in M33, validating imaging techniques and refining star identifications in crowded regions.

Findings

Spectroscopy confirms narrow-band imaging effectiveness for emission-line star detection.

Improved identification of emission-line stars using archival HST images.

Discovery of a new emission-line star in M33.

Abstract

We present optical spectra of 14 emission-line stars in M33s giant HII regions NGC 592, NGC 595 and NGC 604: five of them are known WR stars, for which we present a better quality spectrogram, eight were WR candidates based on narrow-band imagery and one is a serendipitous discovery. Spectroscopy confirms the power of interference filter imagery to detect emission-line stars down to an equivalent width of about 5 A in crowded fields. We have also used archival HST/WFPC2 images to correctly identify emission-line stars in NGC 592 and NGC 588. emission-line stars in NGC 592 and NGC 588.